This application claims the priority of German patent Document 100 47 755.0, filed Sep. 27, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a starter-generator device for internal combustion engines and a method for operating the device.
German Patent DE 19632074 C2 discloses a starting device for internal combustion engines with at least one first nonpositive clutch and a starter-generator that can be actuated by means of an electrical energy source and is in effective connection with a selectable gearbox. The nonpositive clutch is positioned after the flywheel generator and ahead of the gearbox. This has the disadvantage that the generator cannot be switched on to synchronize the gearbox in the state decoupled from the engine and the generator cannot start an engine with a high breakaway torque.
An object of the invention is to design and arrange the starter-generator device in such a way that it is possible to omit components from the drive train and that even engines with a higher starting torque than that of the starter-generator can be started.
According to the invention, this object is achieved by providing at least one nonpositive clutch is provided between a flywheel generator, which can be actuated by means of an electrical energy source, and a combustion engine. The flywheel generator forms the actual centrifugal mass of the combustion engine.
One particular advantage of the invention is that the flywheel generator can break away a combustion engine that has a considerably higher breakaway torque than the torque of the flywheel generator in the starting state with the flywheel generator stationary, in which it would also have to crank the engine from stationary. It is thus also possible to crank the engine from the stationary condition of the engine by means of the already rotating generator.
Another advantage is that the flywheel generator can be used to synchronize the gearbox. When changing up to a higher gear, the gearbox input shaft can be braked by the flywheel generator until the desired rotational speed has been reached.
Another advantage is that almost wear-free operation of the friction clutch between the flywheel generator and the combustion engine is possible because it can be assisted during the process of driving away by the action of the flywheel generator and, given appropriate dimensioning, can be closed almost without a speed difference.
In a preferred development of the invention, specifically in the passenger-car sector, a vehicle can drive either forwards or backwards in first gear, thus making it possible to omit the customary intermediate shaft for reverse gear in a customary change-speed gearbox. This represents a considerable simplification of the gearbox and weight savings in the drive train.
In another advantageous refinement, use is made of a gearbox in which a positive clutch is arranged on the input shaft. In interaction with the flywheel generator, this makes it possible to produce a particularly compact and inexpensive drive train.
Another advantage of the invention is that the flywheel generator can convert braking energy of the vehicle into other types of energy and thus serves as a wear-free brake.
It is furthermore possible to operate the flywheel generator as a starter or a generator respectively, making it possible to omit units.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.